Just to report back that I towed the Series 3 over 600km and it all worked out perfectly. I tow with a Dodge 2500 diesel and it is much heavier than the LR so accelerating and braking were a breeze. It even tracked around tight right hand corners without difficulty. I averaged 100km/h with a max of 110km/h (briefly). I did beef up the safety chains that came with the tow bar pictured above. I wired up plugs that spliced into the rear tail lights and into the trailer hitch plug on the truck. Now I have a wire loom that plugs into the LR in seconds. The tow bar has quick connects so it is easy to install.

I managed a 2.5 level off road trail with no breakages (or even getting stuck). All in all, a smooth trip.